Fermentation, as by aerobic or anaerobic digestion, is used to treat water, such as effluents from industry and municipalities. U.S. Pat. No. 4,672,691, in the name of the present assignees, issued Jun. 16, 1987, describes a bulk volume fermenter in the form of an enclosure having a membrane cover, with means for collecting methane produced by the anaerobic fermentation. In this arrangement the gas is collected in a conduit extending along the top of the containing wall. A central collecting duct is also described.
The present invention provides for various improvements in a bulk volume fermenter, particularly anaerobic fermentation apparatus, applicable to apparatus as described in the above-mentioned patent, but not restricted to such apparatus.